Here's the short explanation of why a pressure cooker can make tender beef stew in 30 minutes instead of two hours and 30 minutes, and why long-grain brown rice takes 20 minutes instead of an hour: PV = nRT.

For most of us, that whisper from the catacombs of memory is saying we last heard that equation in high school physics. It's the Ideal Gas Law, which in fact is not the name of a byproduct of consuming beans made in a pressure cooker.

For the science-challenged, the layman's explanation is that the water in a pressure cooker boils at a higher temperature than the 212-degree threshold in an unsealed pot, meaning food cooks faster. And since minimal steam escapes from a closed pressure cooker, liquid stays in the pot and is forced by pressure into the food, rendering it soft and moist much more quickly than can be achieved by other methods.

Since being invented in the late 1670s by Denis Papin, a French physicist living in London at the time, the pressure cooker has swung widely in popularity. They were so large, difficult to operate and dangerous — prone to exploding and soaking kitchen and cook with superheated food and metal shards — that the first home version wasn't patented until the beginning of the 20th century. Usage surged until the 1940s, when metal previously destined for household uses was redirected to the war effort, and cheap postwar pressure cookers gained a deserved reputation for blowing off lids — so much so that "pressure cooker" became synonymous with an intense and usually undesirable situation.

Pressure cookers today are altogether tamer beasts, with sophisticated locking systems and valve mechanisms for releasing steam; electric pressure cookers adjust the heat automatically to maintain optimum temperature and pressure, and some even self-vent at the end of the preprogrammed cooking time.

Regardless of whether the pressure cooker is Papin's 4-foot-tall cast-iron model with its own furnace or a $25, 4-quart, Presto-brand aluminum pot from Wal-Mart, the principle and results are the same: shorter cooking time and tender, moist food.

A guest at a 1680s dinner of aristocrats and thinkers for which Papin demonstrated his "Digester," as he called it, raved, "The hardest bones of beef itself, and mutton, were made as soft as cheese. ... We ate pike and other fish bones, all without impediment, but nothing exceeded the pigeons, which tasted just as if baked in a pie."

"What you could do with it was something that people had never seen before," said Harold McGee, author of "On Food & Cooking: The Science & Lore of the Kitchen," the definitive tome first published in 1984. Speaking in a lecture last month at George Washington University, he continued, "It was like these people had discovered new vistas, like a new world — not geographically but culinarily."

Her book includes recipes for Arabian Stuffed Swiss Chard (15 minutes), Cuban Black Beans and Sausage (10 minutes) and 5-Minute Walnut Fudge Drops. Such times appear throughout the library of pressure-cooker cookbooks: veal osso bucco in 20 minutes vs. 90, Cornish game hen in 12 minutes instead of five times as long, whole beets in a third of the time of roasted. As Lorna J. Sass puts it in the subtitle of her book "Pressure Perfect," you get "two-hour taste in 20 minutes."

Pressure cookers are also used to can low-acid foods including meat, vegetables and seafood, and it's even possible to bake a cake in a pressure cooker, albeit without using the pressure function. Cookbooks published in developing countries, where many homes lack ovens, advise packing the bottom of the pressure cooker with sand, covering it with a rack and placing the cake pan atop the rack. Putting the covered but not sealed pot on the stove produces radiant heat similar to that in an oven.

There are some tasks a pressure cooker cannot do. A whole chicken may be done and dripping with succulence after 18 minutes in the pressure cooker, but its flabby skin will still need to be blasted in a hot oven to mimic the delectable crispiness of a roasted chicken's skin. Beef, too, will require a post-pressure sear if a crust is desired. Further, since it can take up to 10 minutes for the pressure inside to dissipate and allow the lid to be opened, cooking cannot be monitored nearly as easily as in a stockpot or roasting pan.

And, of course, misused pressure cookers can still explode. On the Feb. 26 episode of the ABC cooking competition "The Taste," one of the contestants, while pressure-cooking a pig head, suffered a pot blowout and giant mess.

It was his fault: Not following standard operating procedure and trying to further hurry the cooking, he left the heat cranked up after pressure had been reached instead of turning down the flame. Despite the disaster, "Taste" competitor Gregg Drusinsky's instinct to use the pressure cooker paid off: His North Carolina head cheese won the round.

Truss chicken and brown on all sides in oil in separate pan on top of stove. Put chicken in cooker, breast side down. Saute carrots and onions in pan on top of stove. Deglaze pan with 1 can chicken broth and add entire contents of saute pan to the cooker. Cut tomatoes into smaller pieces. Add tomatoes with juice to cooker. Add Worcestershire and season with salt, pepper and rosemary or thyme to taste. Top up with water, to fill line inside cooker.

Put cover on cooker and seal. Bring up to pressure then reduce heat and cook for 25 minutes. Open cooker when pressure has dropped. Remove chicken from cooker and remove all meat and skin from the bones. Discard bones and skin. Shred the meat and set aside, keeping warm.

Putting the cooker back on the heat, bring broth and vegetables to a boil. Add pasta and 1 can chicken broth. Cook, uncovered, until pasta is tender. Add chicken. Stir and serve with crusty bread. Ladle into serving bowls and sprinkle with Parmesan or Romano cheese, if desired.

Note: This dish has the consistency of a stew.

From Wolfgang Puck

Alton Brown's Pressure Cooker Chili

Makes 4 servings

3 pounds stew meat (beef, pork, and/or lamb)

2 teaspoons peanut oil

1 1/2 teaspoons kosher salt

1 (12-ounce) bottle of beer, preferably a medium ale

1 (16-ounce) container salsa

30 tortilla chips

2 chipotle peppers canned in adobo sauce, chopped

1 tablespoon adobo sauce (from the chipotle peppers in adobo)

1 tablespoon tomato paste

1 tablespoon chili powder

1 teaspoon ground cumin

Place the meat in a large mixing bowl and toss with the peanut oil and salt. Set aside.

Heat a 6-quart heavy-bottomed pressure cooker over high heat until hot. Add the meat in three or four batches and brown on all sides, 2 minutes per batch. Once each batch is browned, place the meat in a clean large bowl.

Once all of the meat is browned, add the beer to the cooker to deglaze the pot.

Scrape the browned bits from the bottom of the pot. Add the meat back to the pressure cooker along with the salsa, tortilla chips, chipotle peppers, adobo sauce, tomato paste, chili powder and ground cumin; stir to combine. Lock the lid in place according to the manufacturer's instructions. When the steam begins to hiss out of the cooker, reduce the heat to low, just enough to maintain a very weak whistle.

Cook for 25 minutes. Remove from the heat and carefully release the steam. Serve immediately.